In order to contact the electric lines of a measuring sensor, especially of a planar lambda probe, to the lines of a wiring harness usually used in motor-vehicle construction, and to protect this junction from outer influences, it is known to extrusion coat with plastic around the contact joints after making the electrical connection. Since the lambda probe is subject to high temperatures, its electric line is a high-temperature line which is surrounded by an enclosing (sheathing) tube. The individual wires of the sensor are guided in the enclosing tube, insulated from one another in a mineral powder. As mentioned above, the electrical contact joints of the two lines, together with the end area of the enclosing tube, are embedded in the plastic extrusion coat. The transition zone between the enclosing tube and the plastic extrusion coat represents a weak point which, due to environmental influences and especially because of the different materials (metal/plastic), may not remain impervious over the service life, so that moisture and foreign matter can penetrate therein. This can lead to shunts of the electric conductors. It is also possible, viewed over the service life, for the transition zone (enclosing tube, plastic extrusion coat) to be mechanically damaged, resulting in a pulling-apart, twisting, or the like, whereby a breakdown of the sensor functioning can occur.